CVE-2026-54411
Description
A flaw was found in Linux-PAM's pam_userdb module. This vulnerability, categorized as an Observable Timing Discrepancy (CWE-208), allows a local or network-adjacent attacker to recover plaintext passwords. By repeatedly attempting authentication and measuring response-timing differences during plaintext password comparison, an attacker can deduce the password. This flaw is exploitable when the pam_userdb module is configured to store and compare credentials in plaintext, which is not a default setting.
Statement
This Moderate flaw in Linux-PAM's pam_userdb module allows a local or network-adjacent attacker to recover plaintext passwords through a timing discrepancy. This vulnerability requires the pam_userdb module to be explicitly configured to store and compare credentials in plaintext, which is not a default or recommended configuration in Red Hat Enterprise Linux environments. The impact is limited by the need for repeated authentication attempts and specific, non-default module configurations.
Mitigation
To mitigate this issue, administrators should ensure that the `pam_userdb` module is not configured to store or compare credentials in plaintext. Verify that `pam_userdb` is either configured with a strong cryptographic hashing method or, if not required, is disabled. Avoid using `crypt=none` or omitting the `crypt=` argument when configuring `pam_userdb`. If changes are made to PAM configuration files, services relying on PAM may need to be restarted for the changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.8 | N/A | 5.9 |
| Attack Vector | Adjacent Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | Low | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality,Access Control
Technical Impact: Read Application Data; Bypass Protection Mechanism
Frequently Asked Questions
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